diff --git a/src/ol/geom/geometry.js b/src/ol/geom/geometry.js
index 70fac46257..46f69d9115 100644
--- a/src/ol/geom/geometry.js
+++ b/src/ol/geom/geometry.js
@@ -2,10 +2,12 @@ goog.provide('ol.geom.Geometry');
 goog.provide('ol.geom.GeometryLayout');
 goog.provide('ol.geom.GeometryType');
 
+goog.require('goog.asserts');
 goog.require('goog.functions');
 goog.require('ol.Object');
 goog.require('ol.extent');
 goog.require('ol.proj');
+goog.require('ol.proj.Units');
 
 
 /**
@@ -250,6 +252,9 @@ ol.geom.Geometry.prototype.translate = goog.abstractMethod;
  * @api stable
  */
 ol.geom.Geometry.prototype.transform = function(source, destination) {
+  goog.asserts.assert(
+      ol.proj.get(source).getUnits() !== ol.proj.Units.TILE_PIXELS,
+      'cannot transform geometries with TILE_PIXELS units');
   this.applyTransform(ol.proj.getTransform(source, destination));
   return this;
 };
diff --git a/src/ol/proj/proj.js b/src/ol/proj/proj.js
index cfb7c9faa9..193bc838d3 100644
--- a/src/ol/proj/proj.js
+++ b/src/ol/proj/proj.js
@@ -23,7 +23,8 @@ ol.proj.ProjectionLike;
 
 
 /**
- * Projection units: `'degrees'`, `'ft'`, `'m'`, `'pixels'`, or `'us-ft'`.
+ * Projection units: `'degrees'`, `'ft'`, `'m'`, `'pixels'`, `'tile-pixels'` or
+ * `'us-ft'`.
  * @enum {string}
  * @api stable
  */
@@ -32,6 +33,7 @@ ol.proj.Units = {
   FEET: 'ft',
   METERS: 'm',
   PIXELS: 'pixels',
+  TILE_PIXELS: 'tile-pixels',
   USFEET: 'us-ft'
 };